35i with 15K miles. Just drove it 1600 miles to Florida. Average MPG a hair over 23 doing 80 MPHish. Best was 24.6 and worst was 21.7 on trip (obviously has pumps will vary).

When I did the same with a 35d last year it averaged around 24 at similar speeds. (Note this was winter diesel part of the trip).

So not a bad showing by the 35i.

One thing that still amazes me about the 35i. The thing just flies when needed to pass people at higher speeds.